1. Field of the Invention
The present invention relates to a spinneret assembly for conjugate spinning, which has no substantial influence upon a conjugate ratio in the side-by-side type conjugate spinning, even when there is a more or less variation in the relative position between a spinning plate and a distributing plate superposed closely thereupon due to their getting out of order, and can be increased in size to increase the number of spinning holes and hence the spinning efficiency.
2. Statement of the Prior Art
The production of side-by-side type conjugate fibers from two kinds of thermoplastic resins has been carried out for a long time. Year after year, the side-by-side type conjugate fibers (which may be simply called the conjugate fiber or fibers in the description to follow) have enjoyed steadily increased use as staple fibers.
In general, there are mainly two types of the processes for producing the staple fibers. One process involves effecting spinning at a spinning rate of several hundreds to 3,000 meters per minute, bundling the obtained unstretached fibers and temporarily storing them in a container, and thereafter collecting them together to form a thick tow which is then fed to a stretching step in which the required stretching, crimping, heat-treatment and like treatments were applied, followed by cutting and packaging.
The other process involves effecting spinning at a low spinning rate of several meters to several tens meters per minute, and feeding the thus spinned unstretched fibers directly to a stretching step, not through any storing step, in which a succession of treatments such as stretching, crimping, heat-treatment and cutting are continuously carried out (this step will hereinafter be referred to as the continuous type production process).
The continuous type production process is carried out without any interruption between the spinning step and the stretching step, and is more advantageous than the first-mentioned process in that higher yields are achieved, and containers and working area, installation and labor associated therewith are dispensed with, resulting in a recent tendency for conjugate staple fibers to be produced by that continuous type production process.
The principles of the production of conjugate fibers applied in general are that two kinds of thermoplastic resins are independently made molten by heating to prepare independent spinning liquids, the two liquids are separately fed under pressure to the associated spinning holes by way of independent paths, at or just before which they are combined with each other at a predetermined ratio ( of 1:1 in most cases; the following explanation shall typically be made to the conjugate ratio of 1:1), and the combined liquids are spun out of the spinning holes, followed by the given steps.
Reference will now be made to one typical example of the spinneret assembly heretofore used for spinning conjugate fibers with reference to the drawings. The spinneret assembly for spinning conjugate fibers may simply be called the spinneret assembly in the description to follow.
Referring to FIG. 9(a), a spinning plate 1 includes therein a number of spinning holes 2. Usually, the multiplicity of spinning holes 2 are formed in a plurality of rows that are parallel with each other in at least one direction, and are disposed at equal intervals. A distribution plate 8 is superposed on and brought into close contact with the upper face of the spinning plate 1, to which the spinning liquid are to be fed. Of separate spinning liquid paths comprising a number of inlet grooves 9 disposed in parallel so as to receive separately and alternatively two kinds of spinning liquid A and B fed from above and guide paths C for guiding independently the liquid A and B leaving the inlet grooves 9 into the upper openings 2a of the respective spinning holes 2 in the spinning plate 1, at least the guide paths C are provided to the distribution plate 8. It is noted in this connection that a part or whole of each guide path C forms pressure-adjusting means or holes 10. In the assembly of FIG. 9, the inlet grooves 9 are also provided in the distribution plate 8. In the distribution plate 8 used with the conventional spinneret assembly, the endmost portion of guide path C is practically bifurcated in outlet grooves 11 extending over the adjacent two rows of spinning holes 2 of the spinning plate 1, as illustrated in FIG. 9(a). The pressure-adjusting means or holes 10 is then formed between the inlet and outlet grooves 9 and 11 in the guide path C. In this case, the lower end portion of a partition wall 12 for spacing an outlet groove 11 away from the adjacent outlet groove 11 serves to divide an upper open portion 2a of each row of spinning holes 2 at its central portion into equal left and right subportions 2a' and 2a". As illustrated in FIG. 9(a), therefore, the spinning liquid A and B regulated in respect of pressure in the associated guide paths C are fed into one spinning hole 2. Thus the spinning liquid A or B regulated in respect of pressure in one guide path C is branched out at the endmost portion of that guide path C and guided into the adjacent rows of spinning holes 2. In this manner, the two kinds of spinning liquid A and B are spinned out of one spinning hole 2 without being mixed together, thus giving the side-by-side type conjugate structure.
One example of the conventional spinneret assembly having such a main structure as mentioned above will be explained with reference to FIGS. 10 and 11 (corresponding to the sectional direction in FIG. 9). Superposed upon the spinning plate 1 is the distribution plate 8 including therein the inlet grooves 9 to which the two kinds of spinning liquid A and B may individually and alternately be fed according to any of the known techniques. In the example illustrated, a distribution-aiding plate 13, shown in FIG. 12, is placed upon the distribution plate 8 as the auxiliary plate designed to this end, upon which a filter 14 is further superposed for the purpose of removing foreign matters from the spinning liquid. These parts are housed within a spinneret cap 15, as disclosed in FIG. 10. All the parts but the filter 14 are accurately positioned by set pins to locate the lower end portion of the partition wall 12 at the middle of the upper opening portion 2a of the spinning hole 2 of the spinning plate 1. The spinning liquids A and B are respectively fed from the associated inlet ports 15a and 15b formed in the spinneret cap 15, and are stored in left and right top reservoir chambers 16 and 16' defined by a separation wall 15c extending from the inside of the top portion of the cap 15, whence they are supplied to the distribution plate 8 successively through the filter 14 and the distribution-aiding plate 13. The distribution-aiding plate 13 is provided therein with a number of inlet holes 13a, which are of the arrangement that they are divided into the left and right groups along the center line zone thereof, and that, when the distribution-aiding plate 13 is superposed upon the distribution plate 8 with the center line zone crossing at right angles to the inlet grooves 9, such inlet holes 13a are linearly located at the respective positions corresponding to the respective inlet grooves 9, and alternate in the left and right groups. The separation wall 15c of the spinneret cap 15 is allowed to engate at its lower end portion with that center line zone through the filter 14. Consequently, when the two kinds of spinning liquid A and B are individually fed to the distribution plate 8 through the distribution-aiding plate 13, as stated above, they are introduced into the multiplicity of inlet grooves 9 disposed in parallel in the distribution plate 8 in the way of alternating the inlet groove 9 into which spinning liquid A is introduced with the inlet groove 9 into which spinning liquid B is introduced, pass through the pressure adjusting means or holes 10 and outlet grooves 11, and are spinned out of the spinning holes 2 to give a conjugate structure comprising the components A and B.
As the aforesaid conventional spinneret assembly is repeatedly used over an extended period of time, the stack of the spinneret plate 1, the distribution plate 8, the spinneret cap 15 and the like becomes out of order due to the deformation and thinning of the set pins, the distortion and thermal expansion of the spinneret plate 1, the distribution plate 8 and the spinneret cap 15, etc. The result is that the spinneret plate 1 is horizontally displaced with respect to the distribution plate 8, and vice versa. Where such displacement takes place along the lengthwise direction of the partition wall 12, it has not any influence upon the conjugate ratio, since the fiber takes on the same sectional shape as shown in FIG. 9(b),(c). This is because the relation in position between the partition wall 12 of the distribution plate 8 and the spinning hole 2 in the spinneret plate 1 is in a normal state as shown in FIG. 9(a). However, where the displacement occurs in the direction crossing the lengthwise direction of the partition wall 12 of the distribution plate 8, it exerts an influence upon the conjugate ratio, since the relation in position between the partition wall 12 and the spinning hole 2 varies, as shown in FIG. 13(a). Particularly when it is intended to produce the staple fibers of conjugate fibers by the aforesaid continuous process, noticeable influences are exerted upon the conjugate ratio and, in some cases, upon the divided state, i.e., conjugate structure of the composite components A and B in the fiber section. Since the continuous process is of a low productivity per spinning hole 2 due to its low spinning rate, it is required to increase the spinning rate and use as many spinning holes as possible for instance, in the order of several thousands of spinning holes per spinneret assembly. To realize this, the overall size of the spinneret assembly should be increased, thus resulting in an increase in the displacement.
When the positional relation between the partition wall 12 and the spinning hole 2 varies in this manner, there is a variation in the amount of the spinning liquid A or B formed from one outlet groove 11 into the two spinning holes 2 under the same pressure, the above mentioned variation depending upon a variation in the size of the two upper opening subportions 2a' and 2a" positioned on the left and right sides of one spinning hole 2 as shown in FIG. 13(a). Thus, the spinning liquid A and B are forced into one spinning hole 2 in varied amounts. As will be appreciated from FIGS. 13(b) and (c) showing the sections of the fibers upon being spinnned out, therefore, the conjugate ratio of the components A and B does not only depart largely from 1:1, but the conjugate structure is also affected. The prior art spinneret assembly has offered such problems.